This application is related to the subsequent improvements disclosed in the joint application of Michael C. Henke, Gordon D. Bell, Don P. Smith, and Virgil L. Archer entitled "Impingement Oven," Ser. No. 386,609, filed June 9, 1982
In impingement heating and cooling devices for processing foods a jet of either heated or cooled gas impinges upon the surface of the food to sweep away the boundary layer and increase the rate of heat transfer between the gas and the food product. Cooking and cooling devices of this type have proven quite satisfactory and have been combined with other types of cooking apparatus such as microwaves to produce unique combinations of cooking devices. Exemplary prior art impingement devices are found in prior art U.S. Pat. Nos. 3,884,213 and 4,154,861.
In impingement devices used to process foods, the control of the flow of the gases presents problems which are not found in any other type of heating or cooling device. It is apparent that the volume and velocity of the gases contacting the food being processed determine the cooking or cooling rate. It is therefore critical to assure that the gas flow is within the specifications necessary to properly cook or cool the food to insure that the food product is either completely cooked or cooled as the case may be. In addition to the problems of controlling the rate and volume of the flow of the impinging gases in devices of this type, other unique problems are present relating to the flow of these gases which are not present in any other type of heating or cooling device. These problems relate to the distribution of the heating or cooling gas jets across the product to insure that uniform cooking or cooling occurs throughout the entire product. This critical requirement of food processing impingement devices requires that the various jets contacting a food product at a given time operate in a fixed relationship to each other even though variations in the supply flow rate occur. In addition, it has been found that the return flow path of the gases from the impingement jets affects the performance of the oven. In the past, it was believed that the most efficient configuration for removing discharged impingement gases was to draft the gases in a direction transverse to the direction of the flow of the gases in impingement jets, at least, in the area of the food product. Thus, impingement gases would flow from the nozzle and impinge upon the product and after contacting the product would move across the product in a direction transverse the direction of flow of the impingement jets. Although this configuration performed satisfactorily it was found that contrary to what would be expected that the efficiency and performance of the system could be improved by discharging the impingement gases in a direction reverse of the direction of the impingement jets. Thus, it was found by removing as much as possible of the transverse draft of the impingement gases and by causing a discharge in a direction opposite to the direction of the flow of the impingement jets that surprising improvement in the operating characteristics occurred. It is believed that this improved configuration reduced turbulence and increased the uniformity of heating or cooling throughout the device.